Tarihinan Ağyüz
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Calendar Converter
Calendar Converter is a comprehensive guide to understanding different calendar and date systems and how dates are represented across various systems. The article covers the Gregorian and Julian calendars, Hebrew and Islamic calendars, Persian and Mayan calendars, the Bahá'í Calendar, Indian National Calendar, and French Republican Calendar, as well as technical date representations such as Julian Day, ISO 8601, Unix Time, and the Excel serial date system. It explains the basic structures of these calendars, leap-year rules, date formats, and the ways dates are represented and processed in computer systems.
Çoklu Takvim ve Tarih Dönüştürücü
Jülyen Günü (JD) köprüsü üzerinden dünya takvimleri, antik sistemler ve zaman damgaları arasında çift yönlü hassas dönüşüm.
Miladi1 Ocak 2026
Hicri12 Recep 1447
Hafta GünüPerşembe
Jülyen Günü (JD)2461041.50
Miladi Takvim (Gregorian)
Normal YılPerşembe
Uluslararası standart güneş takvimi.
:
2026-01-01 00:00:00
Hicri Takvim (Islamic / Kameri)
Artık Yıl (355g)al-khamis
1 Muharrem 1 H (16 Temmuz 622) başlangıçlı saf ay takvimi.
12 Recep 1447 H
Jülyen Takvimi (Eski Usul / Rumi Kök)
Normal YılM.Ö. 46 Julius Caesar reformu (her 4 yılda bir artık yıl).
19 Aralık 2025 (Jülyen)
Celali / İran Takvimi (Şemsi Hicri)
Artık YılPanjshanbeh
Ömer Hayyam kökenli, 2820 yıllık döngüye sahip hassas güneş takvimi.
12 Dey 1404 (Şemsi)
İbrani Takvimi (Hebrew / Yahudi)
12 Aylık Normal Yıl354 Gün
M.Ö. 3761 başlangıçlı, 19 yıllık Meton döngüsüne sahip luni-solar takvim.
12 Teveth 5786
Guide & Content
Many calendar systems have been developed throughout history and across different cultures. The Gregorian calendar is the most widely used today, but the Julian, Hebrew, Islamic, Persian, Mayan, Bahá'í, Indian National, and French Republican calendars are also important in historical and computational work.
A calendar converter makes it possible to compare a date across different calendar systems and understand the rules behind those systems. Such calculations can be performed directly in a web browser using client-side technologies such as JavaScript.
Gregorian Calendar
The Gregorian calendar is the most widely used calendar system for international and civil purposes today. It was introduced in 1582 during the papacy of Pope Gregory XIII.
Its leap-year rules are:
- Years divisible by 4 are leap years.
- Years divisible by 100 are not leap years.
- Years divisible by 400 are leap years.
Therefore, 2000 was a leap year, while 1900 was not.
A Gregorian year normally contains 365 days and a leap year contains 366 days. The average year length is approximately 365.2425 days.
Julian Day
The Julian Day Number (JDN) is widely used in astronomy and scientific computing to represent dates as consecutive numbers.
The system uses an epoch beginning on January 1, 4713 BCE in the Julian calendar. Because dates are represented numerically, intervals can be calculated through simple addition and subtraction.
The Modified Julian Day (MJD) is obtained by subtracting 2,400,000.5 from the Julian Day Number. It uses midnight on November 17, 1858 UTC as its reference epoch.
Julian Calendar
The Julian calendar was introduced by Julius Caesar in 46 BCE and later refined into its final form.
In the Julian calendar, every year divisible by 4 is a leap year. It does not contain the Gregorian calendar's additional exceptions for years divisible by 100 and 400.
As a result, the average Julian year is 365.25 days and gradually diverges from the solar year.
Hebrew Calendar
The Hebrew calendar is a lunisolar calendar designed to keep lunar months aligned with the seasons.
Leap years occur at specific positions within a 19-year cycle. During a leap year, an additional month is inserted.
Days in the Hebrew calendar begin at sunset.
Islamic Calendar
The Islamic calendar is a lunar calendar consisting of 12 months. Months alternate between 29 and 30 days.
Leap years occur according to a 30-year cycle, with the final month extended by one day during a leap year.
Because the lunar year is shorter than the solar year, Islamic months move approximately 11 days earlier through the seasons each solar year.
For religious purposes, the beginning of a month may be determined by observation of the new crescent Moon.
Persian Calendar
The modern Persian calendar was adopted in 1925. Its first six months contain 31 days, the next five contain 30 days, and the final month contains 29 days in an ordinary year and 30 days in a leap year.
Its leap-year rules use a complex cycle designed to maintain very close alignment with the solar year.
Mayan Calendars
The Maya used several calendar systems:
- Long Count: A long-term cyclical system used for historical dating.
- Haab: A 365-day civil calendar.
- Tzolk'in: A 260-day calendar used primarily for religious purposes.
The Long Count represents time through a hierarchy of cycles. The Haab consists of 18 periods of 20 days followed by five additional days. Since it has no leap-year mechanism, it gradually shifts relative to the seasons.
The Tzolk'in combines a cycle of 13 numbers with 20 day names, producing a 260-day cycle.
Bahá'í Calendar
The Bahá'í calendar is a solar calendar organized around 19 months of 19 days each, with additional days outside the regular months.
The beginning of the year is associated with the spring equinox, and days begin at sunset.
Indian National Calendar
India's National Calendar was standardized for civil purposes in 1957.
It contains 12 months. The first month has 30 days in an ordinary year and 31 in a leap year, followed by five 31-day months and six 30-day months.
Years are numbered according to the Saka Era.
French Republican Calendar
The French Republican Calendar was adopted in 1793 during the French Revolution.
It consists of 12 months of 30 days each, followed by five or six additional days depending on the year.
Each month is divided into three 10-day periods. Napoleon abolished the calendar in 1806, after which France returned to the Gregorian calendar.
ISO 8601
ISO 8601 is an international standard for representing dates and times in an unambiguous and machine-readable format.
The most common date format is:
YYYY-MM-DD
For example:
2000-02-29
ISO week dates use a year and week number:
2000-W09-2
A date can also be represented by its day number within the year:
YYYY-DDD
For example:
2000-060
These formats make dates easier to sort, exchange, and process across different countries and computer systems.
Unix Time
Unix time represents the number of seconds elapsed since January 1, 1970 at 00:00:00 UTC.
It is widely used in software systems for storing, comparing, and transmitting dates and times as numeric values.
The traditional signed 32-bit Unix timestamp reaches its limit on January 19, 2038. Modern systems can avoid this limitation by using wider integer representations.
Excel Serial Date System
Microsoft Excel stores dates as serial numbers.
In the PC 1900 date system, January 1, 1900 is used as the starting point. However, for historical compatibility, Excel treats 1900 as a leap year and therefore recognizes February 29, 1900 in its serial date system even though that date did not exist.
This special case must be considered when converting Excel dates to other date systems.
Excel also supports a separate 1904 date system, historically used on Macintosh systems. Its starting point is January 1, 1904.
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